Spark plug



F. A. 0ST

SPARK PLUG Oct. 13; 1942.

Filed June 10, 1940 II\'\ 'ENTOR,

Patented Oct. 13 1942 UNITED STATES PATENT OFFICE SPARK PLUG Frederick A. st, Los Angeles, Calif. Application June 10, 1940, Serial No. 339,647

9 Claims.

This invention relates to spark articularly although not exclusively to that type which is adapted for dependable and economical use on aeroplane engines. A common source of trouble with spark plugs results from a coat of above objections are overcome or materially reduced.

Among further advantages attained by my invention may be mentioned the following:

1. A spark lug that assures a clean spark so as to immediately ignite said mixture.

3. A spark plug which will withstand extremes of heat and cold without cracking, breaking or leaking gas.

and cleaning and which tive reassembling of parts by skilled or unskilled To these ends my invention comprises the features of construction and combination of parts hereinafter described and claimed.

In the drawing, Fig. 1 is cular abutment ring; Fig. 6 is a section of a detail taken on line B6 of Fig. 5; Fig. 7 is a plan of the split abutment ring; Fig. 8 is a section of a detail on line 8-8 of Fig. 7; and Fig. 9 is a vertical section of a portion of a spark plug showing a modified form of my invention.

In the drawing A indicates themetallic shell of my improved spark plug which is externally threaded at ID on its inner end toscrew into the usual threaded spark plug of the shell is passaged longitudinally at 13, the outer end being longer in diameter than the inner portion and internally threaded at M for engagement by theexternal threads l5 of a bushing B, to be hereinafter described. The

' ner.

thus removed the springing the shoes split abutment collar 23 being interposed between and engaging the bushing and insulating core. The abutment ring is formed with a beveled inner face 24 facing forwardly towards the outer end of the spark plug. The split abutment collar is in two halves spaced circumferentially slightly apart and engages the insulating core against a shoulder formed by an annular recess 25 in the insulating core and has an outer circumferential inwardly beveled end 26 pointed inwardly and engagingthe corresponding beveled surface of the annular abutment ring 22. Thus by screwing the bushing outwardly the core is tightened upon its seat to joint between the insulating core and the shell. By screwing ment collar can be removed by lifting its segments out of the annular groove'25, thus'r'eleasing the insulating core and permitting its removal from the shell.

The opposed electric terminal D, :which operates with terminal [S m-producing: the: spark gap is forme'd'ifrom a stamping .(see "Fig. 4) resembling a cage having' a-ring f28 'andx'radiating arms 29, the latter ends concentric 'withthe-icenter:of the ring. These arms29 are bentupwardlyzabove, :outwardly and down with their ishoesierrgaging in detentures'3l in the side 'walllof theinner' iend of the insulating'plug. Theendsof the arms-2'9 and shoes 30 are held tightlyimpressed byithe insulating core 0 in close: contact lwithltheinner wall of the passage" f3 in shellAtol'prodllceelectrical connection with the shellfthe latter .forming one of the electrical terminals by contact with the'wall of the enginefcylinder in the usual manner. The-opposite external electrical' terminal is adapted to'be made-with the outer threaded end'of the'spindlel 8 in the usualman- Normally the terminal ring slightly and evenly'above the annular shoulder 2 I on the terminal" head l'9'so that upon becoming energized a "fat 1 spark is produced between the terminals thus formed without carbon'collecting to reduce the efliciency of the'discharge. "The central opening in ring 28 of'the 'spark-gap'terminal and the dished head whichior-msthe' annular rim 2| of the"companion spark'gap terminal producing a passage by which the gas'mixture enters and mushrooms radially throughthe spark gap and automatically scavenges the-spark terminals, thereby providing'a fresh and immediate contact of gas mixture in' the gapfor ignition and preventing fouling of the spark 's'g-ap terminals. This is extremely importantior' it increases the efiectiveness of ignition. Also the spark gapterminal ring 28 andcompanion terminal head l9 project beyond the'spark plug shell A, thus afiording-a'better exposure of the-spark in a position wherein'the gas mixture has immediate contact with the" spark. The terminal head l9and terminal ring 28 afiord a large surface exposure which increases the likel'ihoo'dof the production of an efiective spark without-any danger from interrupted" ignition. "The dished terminal head also' has an annular groove l9 in its side wall which tends to produce -an inward, upward and outward eddy of" the "gas mixture to additionally scavenge the spa'rkgapterminals and prevent fouling. easily dismantled by screwing the bushing inwardly, removing-the split collar 23 and sliding the insulating 'core 0- out of the shell. When terminal-D can be removed by 30 out" from engagement'wi'th produce a leak-proof having' 'shoessworttheirrouter T 28 is spaced The spark plug-can be those 'a above set forth within the scope 'following claims.

extending inwardly the insulating plug and a new replacement made or the parts can be cleaned. The abutment rings which are connected by conical shoulders and loosely seated permit the self-centering of the core so that the conical shoulders between the core and shell seat closely when drawn tightly by the bushing.

In the construction shown in Fig. 9, the insulating core E is shown seated in the shell F by the inward thrust of .thethreaded bushing G insteadof by the outward pull as-shown in Fig. l and the spark gap terminal cage H, similar to terminal D, is engaged with the wall of the shell by out-turned shoes J instead of in-turned shoes *as in the preferred construction and the inner tapering endof the insulating core E engages the shoes by a wedging action and holds the arms pressed outwardly to produce close electrical connection with the shell and hold the terminal I rigidly spaced at suitable interval from the spark terminal H to produce anaeiiectivezsparkgap.

Where I have used the terms fring 301' ".annulus' in the abovextdescription and -claims:following,-as appliedto theipart 28 of'terminal D, I mean to include =anysuitable:ishape constituting a band containing an inner opening through which gases .may'circulate for scavenging the'spa'rk'gap terminals ormore 'eifectively contacting the'i uel mixture with the ignition spark.

In accordance with the patent statutes, I have described the principles of .toperation .of'my invention together with the-constructionzthereof which I'now consider to represent the .best embodiment thereof 2 but I-',desire :to have it .understood that the' structureshown :is 'only: illustrative .andthat the invention zcanribe carried out by other means-'andfappliedfto uses: other than of the I claim:

1. A.sparkplug,*comprisinggan outer electric conducting shell .having -aninner vlongitudinal tapering shoulden'an insulating: core :having a corresponding outer tapering 'IShOllldBI adapted to seat against said innentaperingshoulder, a bushing threaded in. said; shell adapted to force said core longitudinally'withits:tapering shoulder seated tightly against the stapering a shoulder of said shell, a conducting spindle extending longitudinally'through said core'having a spark gap terminal on its inner endyand arterminal cage having an annular spark gap terminal in juxtaposition to said spark gap'terminalon saidspindle and a support'formingan:electric conductor extending rearwardly from 1 said annular spark gap terminal andsecured in contact between the adjacent surfaces of'said conducting shell-and said insulating core.

2. In a structure as-definedv in claim 1, the terminal cage having a plurality of supporting-arms extending rearwardly and secured incontact between the adjacent surfacesof said conducting shell and said insulating core.

3. In a structure as defined in claim 1, the terminal cage having a plurality of supporting arms between said shell and insulating core having shoes seated in and engaged with said ins lating core and. adapted to be clamped in contact between the shelland core when the core is seated in said'shell.

4. A spark plug,'comprising, an:.0uter electric conducting shell having: an 2 innen'shoulder tapering inwardly, an .insulating :core having-an outer corresponding shoulder tapering inwardly and adapted 1 to seat "tightly :upon 2 said inner shoulder, a bushing sorewthreaded in said shell, an abutment element separately mounted upon the outer end of said insulating core with which said bushing is adapted to engage when unscrewed to tightly seat the tapering shoulders of the shell and insulating core, an electrical conducting spindle extending longitudinally through said core having a spark gap terminal on its inner end and a terminal cage having an annular spark gap terminal in juxtaposition to said first spark gap terminal and a supporting member forming an electrical conductor secured to said insulating core, whereby the pair of spark gap terminals are united with said insulating core as a single assemblage, said support being held in electrical contact with said shell by said insulating core.

5. In a structure as defined in claim 4, the abutment element consisting of a segmental ring and the insulating core having an annular groove in which said segmental ring is adapted to be assembled in position to be engaged by the outward screw movement of said bushing to draw the insulating core tightly seated in said shell.

6. In a structure as defined in claim 4, an abutment element comprising two cooperating encircling rings connected by bevels, one of the abutment elements consisting of a segmental ring and the insulating core having an annular groove in which said segmental ring is adapted to be assembled in position to engage said core and the other engaging said shell and adapted to draw the core and shell tightly together by the outward screw movement of said bushing.

7. A spark plug, comprising, an outer electrical conducting shell having an inner longitudinal tapering shoulder, an insulating core having a corresponding outer tapering shoulder adapted to seat against said inner tapering shoulder, a bushing threaded in said shell adapted to force said core longitudinally with its tapering shoulder seated tightly against the tapering shoulder of said shell, a conducting spindle extending longitudinally through said core having a spark gap terminal on its inner end, and a cage having an annular spark gap terminal and a support forming an electrical conductor extending rearwardly therefrom and secured in contact between the adjacent surfaces of said conducting shell and said insulating core, the spark gap terminal on the inner end of said spindle comprising a dished head in juxtaposition to and spaced from said annular terminal to form a passageway through which gases may circulate and mushroom radially between and scavenge said terminals.

8. A spark plug, comprising, an outer electrical conducting shell having an inner longitudinal tapering shoulder, an insulating core having a corresponding outer tapering shoulder adapted to seat against said inner tapering shoulder, a bushing threaded in said shell adapted to force said core longitudinally with its tapering shoulder seated tightly against the tapering shoulder of said shell, a conducting spindle extending longitudinally through said core having a spark gap terminal on its inner end, and a cage having an annular spark gap terminal and a support forming an electrical conductor extending rearwardly therefrom and secured in contact between the adjacent surfaces of said conducting shell and said insulating core, the spark gap terminal on the inner end of said spindle comprising a head having an annular groove in its side wall and in cooperation with said companion annular terminal tending to produce an inward, upward and outward eddy of the gas to assist in scavenging the spark gap terminals.

9. A spark plug, comprising, an outer electrical conducting shell having an inner seat, an insulating core having a body adapted to close upon said seat, a bushing threaded in said shell adapted to hold said core with its body tightly seated, a central inner electrode extending longitudinally through and provided with a terminal head exposed on the spark gap end of said core and having a concave exposed end and an annular grooved side wall, and an outer terminal cage having a terminal band and means for supportiig the band on the inner end of said shell in juxtaposition over the rim of the inner terminal head to provide a central duct through which the gases are mushroomed radially by said concave inner end of the central electrode and are caused to produce an inward, upward and outward eddy by said annular grooved side wall of the central electrode to effectively scavenge the spark gap terminals and prevent fouling.

FREDERICK A. 0ST 

